Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm…

…/linux/kernel/git/tip/tip into next

Pull core locking updates from Ingo Molnar:
 "The main changes in this cycle were:

   - reduced/streamlined smp_mb__*() interface that allows more usecases
     and makes the existing ones less buggy, especially in rarer
     architectures

   - add rwsem implementation comments

   - bump up lockdep limits"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
  rwsem: Add comments to explain the meaning of the rwsem's count field
  lockdep: Increase static allocations
  arch: Mass conversion of smp_mb__*()
  arch,doc: Convert smp_mb__*()
  arch,xtensa: Convert smp_mb__*()
  arch,x86: Convert smp_mb__*()
  arch,tile: Convert smp_mb__*()
  arch,sparc: Convert smp_mb__*()
  arch,sh: Convert smp_mb__*()
  arch,score: Convert smp_mb__*()
  arch,s390: Convert smp_mb__*()
  arch,powerpc: Convert smp_mb__*()
  arch,parisc: Convert smp_mb__*()
  arch,openrisc: Convert smp_mb__*()
  arch,mn10300: Convert smp_mb__*()
  arch,mips: Convert smp_mb__*()
  arch,metag: Convert smp_mb__*()
  arch,m68k: Convert smp_mb__*()
  arch,m32r: Convert smp_mb__*()
  arch,ia64: Convert smp_mb__*()
  ...

Documentation/atomic_ops.txt

@@ -285,15 +285,13 @@ If a caller requires memory barrier semantics around an atomic_t
 operation which does not return a value, a set of interfaces are
 defined which accomplish this:
 
-	void smp_mb__before_atomic_dec(void);
-	void smp_mb__after_atomic_dec(void);
-	void smp_mb__before_atomic_inc(void);
-	void smp_mb__after_atomic_inc(void);
+	void smp_mb__before_atomic(void);
+	void smp_mb__after_atomic(void);
 
-For example, smp_mb__before_atomic_dec() can be used like so:
+For example, smp_mb__before_atomic() can be used like so:
 
 	obj->dead = 1;
-	smp_mb__before_atomic_dec();
+	smp_mb__before_atomic();
 	atomic_dec(&obj->ref_count);
 
 It makes sure that all memory operations preceding the atomic_dec()
@@ -302,15 +300,10 @@ operation.  In the above example, it guarantees that the assignment of
 "1" to obj->dead will be globally visible to other cpus before the
 atomic counter decrement.
 
-Without the explicit smp_mb__before_atomic_dec() call, the
+Without the explicit smp_mb__before_atomic() call, the
 implementation could legally allow the atomic counter update visible
 to other cpus before the "obj->dead = 1;" assignment.
 
-The other three interfaces listed are used to provide explicit
-ordering with respect to memory operations after an atomic_dec() call
-(smp_mb__after_atomic_dec()) and around atomic_inc() calls
-(smp_mb__{before,after}_atomic_inc()).
-
 A missing memory barrier in the cases where they are required by the
 atomic_t implementation above can have disastrous results.  Here is
 an example, which follows a pattern occurring frequently in the Linux
@@ -487,26 +480,26 @@ Finally there is the basic operation:
 Which returns a boolean indicating if bit "nr" is set in the bitmask
 pointed to by "addr".
 
-If explicit memory barriers are required around clear_bit() (which
-does not return a value, and thus does not need to provide memory
-barrier semantics), two interfaces are provided:
+If explicit memory barriers are required around {set,clear}_bit() (which do
+not return a value, and thus does not need to provide memory barrier
+semantics), two interfaces are provided:
 
-	void smp_mb__before_clear_bit(void);
-	void smp_mb__after_clear_bit(void);
+	void smp_mb__before_atomic(void);
+	void smp_mb__after_atomic(void);
 
 They are used as follows, and are akin to their atomic_t operation
 brothers:
 
 	/* All memory operations before this call will
 	 * be globally visible before the clear_bit().
 	 */
-	smp_mb__before_clear_bit();
+	smp_mb__before_atomic();
 	clear_bit( ... );
 
 	/* The clear_bit() will be visible before all
 	 * subsequent memory operations.
 	 */
-	 smp_mb__after_clear_bit();
+	 smp_mb__after_atomic();
 
 There are two special bitops with lock barrier semantics (acquire/release,
 same as spinlocks). These operate in the same way as their non-_lock/unlock

Documentation/memory-barriers.txt

@@ -1583,20 +1583,21 @@ There are some more advanced barrier functions:
      insert anything more than a compiler barrier in a UP compilation.
 
 
- (*) smp_mb__before_atomic_dec();
- (*) smp_mb__after_atomic_dec();
- (*) smp_mb__before_atomic_inc();
- (*) smp_mb__after_atomic_inc();
+ (*) smp_mb__before_atomic();
+ (*) smp_mb__after_atomic();
 
-     These are for use with atomic add, subtract, increment and decrement
-     functions that don't return a value, especially when used for reference
-     counting.  These functions do not imply memory barriers.
+     These are for use with atomic (such as add, subtract, increment and
+     decrement) functions that don't return a value, especially when used for
+     reference counting.  These functions do not imply memory barriers.
+
+     These are also used for atomic bitop functions that do not return a
+     value (such as set_bit and clear_bit).
 
      As an example, consider a piece of code that marks an object as being dead
      and then decrements the object's reference count:
 
 	obj->dead = 1;
-	smp_mb__before_atomic_dec();
+	smp_mb__before_atomic();
 	atomic_dec(&obj->ref_count);
 
      This makes sure that the death mark on the object is perceived to be set
@@ -1606,27 +1607,6 @@ There are some more advanced barrier functions:
      operations" subsection for information on where to use these.
 
 
- (*) smp_mb__before_clear_bit(void);
- (*) smp_mb__after_clear_bit(void);
-
-     These are for use similar to the atomic inc/dec barriers.  These are
-     typically used for bitwise unlocking operations, so care must be taken as
-     there are no implicit memory barriers here either.
-
-     Consider implementing an unlock operation of some nature by clearing a
-     locking bit.  The clear_bit() would then need to be barriered like this:
-
-	smp_mb__before_clear_bit();
-	clear_bit( ... );
-
-     This prevents memory operations before the clear leaking to after it.  See
-     the subsection on "Locking Functions" with reference to RELEASE operation
-     implications.
-
-     See Documentation/atomic_ops.txt for more information.  See the "Atomic
-     operations" subsection for information on where to use these.
-
-
 MMIO WRITE BARRIER
 ------------------
 
@@ -2283,11 +2263,11 @@ operations:
 	change_bit();
 
 With these the appropriate explicit memory barrier should be used if necessary
-(smp_mb__before_clear_bit() for instance).
+(smp_mb__before_atomic() for instance).
 
 
 The following also do _not_ imply memory barriers, and so may require explicit
-memory barriers under some circumstances (smp_mb__before_atomic_dec() for
+memory barriers under some circumstances (smp_mb__before_atomic() for
 instance):
 
 	atomic_add();

arch/alpha/include/asm/atomic.h

@@ -292,9 +292,4 @@ static inline long atomic64_dec_if_positive(atomic64_t *v)
 #define atomic_dec(v) atomic_sub(1,(v))
 #define atomic64_dec(v) atomic64_sub(1,(v))
 
-#define smp_mb__before_atomic_dec()	smp_mb()
-#define smp_mb__after_atomic_dec()	smp_mb()
-#define smp_mb__before_atomic_inc()	smp_mb()
-#define smp_mb__after_atomic_inc()	smp_mb()
-
 #endif /* _ALPHA_ATOMIC_H */

arch/alpha/include/asm/bitops.h

@@ -53,9 +53,6 @@ __set_bit(unsigned long nr, volatile void * addr)
 	*m |= 1 << (nr & 31);
 }
 
-#define smp_mb__before_clear_bit()	smp_mb()
-#define smp_mb__after_clear_bit()	smp_mb()
-
 static inline void
 clear_bit(unsigned long nr, volatile void * addr)
 {

arch/arc/include/asm/atomic.h

@@ -190,11 +190,6 @@ static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
 
 #endif /* !CONFIG_ARC_HAS_LLSC */
 
-#define smp_mb__before_atomic_dec()	barrier()
-#define smp_mb__after_atomic_dec()	barrier()
-#define smp_mb__before_atomic_inc()	barrier()
-#define smp_mb__after_atomic_inc()	barrier()
-
 /**
  * __atomic_add_unless - add unless the number is a given value
  * @v: pointer of type atomic_t

arch/arc/include/asm/bitops.h

@@ -19,6 +19,7 @@
 
 #include <linux/types.h>
 #include <linux/compiler.h>
+#include <asm/barrier.h>
 
 /*
  * Hardware assisted read-modify-write using ARC700 LLOCK/SCOND insns.
@@ -496,10 +497,6 @@ static inline __attribute__ ((const)) int __ffs(unsigned long word)
  */
 #define ffz(x)	__ffs(~(x))
 
-/* TODO does this affect uni-processor code */
-#define smp_mb__before_clear_bit()  barrier()
-#define smp_mb__after_clear_bit()   barrier()
-
 #include <asm-generic/bitops/hweight.h>
 #include <asm-generic/bitops/fls64.h>
 #include <asm-generic/bitops/sched.h>

arch/arm/include/asm/atomic.h

@@ -241,11 +241,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 
 #define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)
 
-#define smp_mb__before_atomic_dec()	smp_mb()
-#define smp_mb__after_atomic_dec()	smp_mb()
-#define smp_mb__before_atomic_inc()	smp_mb()
-#define smp_mb__after_atomic_inc()	smp_mb()
-
 #ifndef CONFIG_GENERIC_ATOMIC64
 typedef struct {
 	long long counter;

arch/arm/include/asm/barrier.h

@@ -79,5 +79,8 @@ do {									\
 
 #define set_mb(var, value)	do { var = value; smp_mb(); } while (0)
 
+#define smp_mb__before_atomic()	smp_mb()
+#define smp_mb__after_atomic()	smp_mb()
+
 #endif /* !__ASSEMBLY__ */
 #endif /* __ASM_BARRIER_H */

arch/arm/include/asm/bitops.h

@@ -25,9 +25,7 @@
 
 #include <linux/compiler.h>
 #include <linux/irqflags.h>
-
-#define smp_mb__before_clear_bit()	smp_mb()
-#define smp_mb__after_clear_bit()	smp_mb()
+#include <asm/barrier.h>
 
 /*
  * These functions are the basis of our bit ops.

arch/arm64/include/asm/atomic.h

@@ -152,11 +152,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 
 #define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)
 
-#define smp_mb__before_atomic_dec()	smp_mb()
-#define smp_mb__after_atomic_dec()	smp_mb()
-#define smp_mb__before_atomic_inc()	smp_mb()
-#define smp_mb__after_atomic_inc()	smp_mb()
-
 /*
  * 64-bit atomic operations.
  */

arch/arm64/include/asm/barrier.h

@@ -98,6 +98,9 @@ do {									\
 #define set_mb(var, value)	do { var = value; smp_mb(); } while (0)
 #define nop()		asm volatile("nop");
 
+#define smp_mb__before_atomic()	smp_mb()
+#define smp_mb__after_atomic()	smp_mb()
+
 #endif	/* __ASSEMBLY__ */
 
 #endif	/* __ASM_BARRIER_H */

arch/arm64/include/asm/bitops.h

@@ -17,17 +17,8 @@
 #define __ASM_BITOPS_H
 
 #include <linux/compiler.h>
-
 #include <asm/barrier.h>
 
-/*
- * clear_bit may not imply a memory barrier
- */
-#ifndef smp_mb__before_clear_bit
-#define smp_mb__before_clear_bit()	smp_mb()
-#define smp_mb__after_clear_bit()	smp_mb()
-#endif
-
 #ifndef _LINUX_BITOPS_H
 #error only <linux/bitops.h> can be included directly
 #endif

arch/avr32/include/asm/atomic.h

@@ -183,9 +183,4 @@ static inline int atomic_sub_if_positive(int i, atomic_t *v)
 
 #define atomic_dec_if_positive(v) atomic_sub_if_positive(1, v)
 
-#define smp_mb__before_atomic_dec()	barrier()
-#define smp_mb__after_atomic_dec()	barrier()
-#define smp_mb__before_atomic_inc()	barrier()
-#define smp_mb__after_atomic_inc()	barrier()
-
 #endif /*  __ASM_AVR32_ATOMIC_H */

arch/avr32/include/asm/bitops.h

@@ -13,12 +13,7 @@
 #endif
 
 #include <asm/byteorder.h>
-
-/*
- * clear_bit() doesn't provide any barrier for the compiler
- */
-#define smp_mb__before_clear_bit()	barrier()
-#define smp_mb__after_clear_bit()	barrier()
+#include <asm/barrier.h>
 
 /*
  * set_bit - Atomically set a bit in memory
@@ -67,7 +62,7 @@ static inline void set_bit(int nr, volatile void * addr)
  *
  * clear_bit() is atomic and may not be reordered.  However, it does
  * not contain a memory barrier, so if it is used for locking purposes,
- * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
+ * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
  * in order to ensure changes are visible on other processors.
  */
 static inline void clear_bit(int nr, volatile void * addr)

arch/blackfin/include/asm/barrier.h

@@ -27,6 +27,9 @@
 
 #endif /* !CONFIG_SMP */
 
+#define smp_mb__before_atomic()	barrier()
+#define smp_mb__after_atomic()	barrier()
+
 #include <asm-generic/barrier.h>
 
 #endif /* _BLACKFIN_BARRIER_H */

arch/blackfin/include/asm/bitops.h

@@ -27,21 +27,17 @@
 
 #include <asm-generic/bitops/ext2-atomic.h>
 
+#include <asm/barrier.h>
+
 #ifndef CONFIG_SMP
 #include <linux/irqflags.h>
-
 /*
  * clear_bit may not imply a memory barrier
  */
-#ifndef smp_mb__before_clear_bit
-#define smp_mb__before_clear_bit()	smp_mb()
-#define smp_mb__after_clear_bit()	smp_mb()
-#endif
 #include <asm-generic/bitops/atomic.h>
 #include <asm-generic/bitops/non-atomic.h>
 #else
 
-#include <asm/barrier.h>
 #include <asm/byteorder.h>	/* swab32 */
 #include <linux/linkage.h>
 
@@ -101,12 +97,6 @@ static inline int test_and_change_bit(int nr, volatile unsigned long *addr)
 	return __raw_bit_test_toggle_asm(a, nr & 0x1f);
 }
 
-/*
- * clear_bit() doesn't provide any barrier for the compiler.
- */
-#define smp_mb__before_clear_bit()	barrier()
-#define smp_mb__after_clear_bit()	barrier()
-
 #define test_bit __skip_test_bit
 #include <asm-generic/bitops/non-atomic.h>
 #undef test_bit

arch/c6x/include/asm/bitops.h

@@ -14,14 +14,8 @@
 #ifdef __KERNEL__
 
 #include <linux/bitops.h>
-
 #include <asm/byteorder.h>
-
-/*
- * clear_bit() doesn't provide any barrier for the compiler.
- */
-#define smp_mb__before_clear_bit() barrier()
-#define smp_mb__after_clear_bit()  barrier()
+#include <asm/barrier.h>
 
 /*
  * We are lucky, DSP is perfect for bitops: do it in 3 cycles

arch/cris/include/asm/atomic.h

@@ -7,6 +7,8 @@
 #include <linux/types.h>
 #include <asm/cmpxchg.h>
 #include <arch/atomic.h>
+#include <arch/system.h>
+#include <asm/barrier.h>
 
 /*
  * Atomic operations that C can't guarantee us.  Useful for
@@ -151,10 +153,4 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 	return ret;
 }
 
-/* Atomic operations are already serializing */
-#define smp_mb__before_atomic_dec()    barrier()
-#define smp_mb__after_atomic_dec()     barrier()
-#define smp_mb__before_atomic_inc()    barrier()
-#define smp_mb__after_atomic_inc()     barrier()
-
 #endif